Re: [PATCH] mm/page_alloc: fix memalloc_nocma_{save/restore} APIs

[Vlastimil Babka <vbabka@suse.cz>]

On 7/21/20 2:05 PM, Matthew Wilcox wrote:
> On Tue, Jul 21, 2020 at 12:28:49PM +0900, js1304@gmail.com wrote:
>> +static inline unsigned int current_alloc_flags(gfp_t gfp_mask,
>> +					unsigned int alloc_flags)
>> +{
>> +#ifdef CONFIG_CMA
>> +	unsigned int pflags = current->flags;
>> +
>> +	if (!(pflags & PF_MEMALLOC_NOCMA) &&
>> +		gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
>> +		alloc_flags |= ALLOC_CMA;
> 
> Please don't indent by one tab when splitting a line because it looks like
> the second line and third line are part of the same block.  Either do
> this:
> 
> 	if (!(pflags & PF_MEMALLOC_NOCMA) &&
> 	    gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
> 		alloc_flags |= ALLOC_CMA;
> 
> or this:
> 	if (!(pflags & PF_MEMALLOC_NOCMA) &&
> 			gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
> 		alloc_flags |= ALLOC_CMA;

Ah, good point.

>> @@ -4619,8 +4631,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>>  		wake_all_kswapds(order, gfp_mask, ac);
>>  
>>  	reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
>> -	if (reserve_flags)
>> +	if (reserve_flags) {
>>  		alloc_flags = reserve_flags;
>> +		alloc_flags = current_alloc_flags(gfp_mask, alloc_flags);
>> +	}
> 
> Is this right?  Shouldn't you be passing reserve_flags to
> current_alloc_flags() here?  Also, there's no need to add { } here.

Note the "alloc_flags = reserve_flags;" line is not being deleted here. But if
it was, your points would be true, and yeah it would be a bit more tidy.